Referring to FIG. 1, Taiwanese Utility Model Patent No. M408023 discloses a conventional support assembly 1 for mounting a solar panel unit 10. The conventional support assembly 1 includes a supporting frame 12, two supporting brackets 11 that are connected to the supporting frame 12, and two supporting rods 13 (only one is shown in FIG. 1 due to the view angle) each interconnecting the corresponding supporting bracket 11 and the supporting frame 12 such that the supporting frame 12 is inclined. The supporting frame 12 is configured for mounting the solar panel unit 10. The supporting brackets 11 are adapted to be mounted on a ground (not shown). However, since the contact area between the supporting brackets 11 and the ground is relatively small, the solar panel unit 10 cannot be firmly mounted on the ground if the ground surface is not flat. Therefore, a flat cement ground has to be built in advance. Since the support assembly 1 has to be transported along with the cement, the transporting cost is relatively high. Moreover, when the support assembly 1 has to be removed, the cement ground also has to be torn down. To tear down the cement ground results in waste of time and cost.